thomson



J. THOMSON.

ELECTRIC FURNACE FOR FUSING METALS CONTAINED IN CRUCIBLES. APPLICATION FILED NOV. a0. 1918.

1,308,880. Patented July 8, 1919.

2 SHEETSSHEET l.

u u z *1 n W 3 R i *Y 3 F4 2 Q a J INVENTOH' M W A TTORNE K5 1. THOMSON. ELECTRIC FURNACE F 0R FUSING METAL 1,308,880

S CONTAINED-IN CRUCIBLES.

APPLICATION FILED NOV- 30.1918.

INVE/VTUR 7W Patented July 8, 1919.

2 SHEETS-SHEET 2.

M .JMMO

A TTO/M/EVS JOHN THOMSON, 0! NEW YORK, N. Y.

- ELECTBIG FURNACE FOR FUSING METALS CONTAINED IN CBUCIBLES.

I Specification of Letters Patent.

Patented July 8, 1919,

Application filed November 30, 1918. Serial No. 264,771.

' To all whom it may concern:

Be it known that 1, JOHN TnoMsoN, a citi' zen of the United States, and a resident of the borough of Manhattan, cit of New York, county and State of New ork, have invented certain new and useful Improvements in Electric Furnaces for Fusing Metals Contained in Crucibles, of which the following is a specification.

This is an invention in electric furnaces for fusing metals contained in crucibles.

The thermal element of the furnace is a carbon resistor of the zig-zag type, and among the objects to be attained the following may especially be mentioned: high thermal e ciency; the utmost simplicity; low cost of constructipn; increased endurance in the crucibles relative to those employed in fuel fired chambers and maintenance of the modes of manipulation usual in established foundry practice.

An effective embodiment of the invention is depicted in the accompanying drawings, constituting a part of this speclfication, in which Figure 1 is a transverse center section of the furnace and v Fig. 2 is a longitudinal center section thereof.

In the furnace, B,is a rectangular chamber, C, and disposed along the bottom there: of is a carbon, zig-zag resistor, D, preferably supported on blocks, E, whose terminals, as F, are connected in the usual manner to a power-circuit, which it necessary to here illustrate.

thereof, that portion of the resistor in which- An ordinary crucible, or a plurality thereof, asG, H, I, are set upon the resistor, either in direct, physical contact therewith or upon interposed refractory lates, as J. The top of the chamber is inc osed in any suitable manner as by means of slabs, K, upon which bricks, as L, may be stacked to obtain an adequate heat insulation.

The distinctly preferable design of resistor for the present mode of functioning is that in which one of its faces has a hi her current-density than the opposite ace,

wheregy the connecting sides are vertically inclin as 'r, 8. Thus, in the present mode of use, the surfaceof higher densi is at the top, upon which the crucibles ei her .directly or indirectly rest. As a. consequence the highest'temperature is developed impinges upon the bottoms of the crucibles.

' plates,

has not been deemed The lower sides of the chamber are sloped, as M, N, the determining angle thereof being such as to upwardly and inwardly refract the heat which flows from the sloped sides of the resistor, as denoted by the arrows a,

0 and m, n.

It might well be supposed, at first thought, that when the so-called graphite crucibles of commerce are set upon the resistor various of its zig-zag but suchis not the case, to any objectionable extent, the reason being that normal raphite crucibles contain such a consi erable portion of clay that their electric resistance is much greater than the practically pure carbon resistor. Yet, when the short-circuiting, or shuntage, might be detrimental, as when employing crucibles machined from blocks of graphetized carbon, the interposed J, would then be formed from refractory material non-conductive to electricity.

'As these plates may be quite thin, they interpose but nominal obstruction to transfer of heat; they also serve to protect the resistor from abrasive 'action, when inserting or re.- moving the crucibles.

Should a crucible fracture, whereby its charge would escape, provision is made to quickly evacuate it, without injuring the resistor, by forming openings, as h, in the supporting blocks, E, and providing an emergency tap, as P, in an end-wall of the chamber.

Inspection of Fig. 1 will clearly denotecording to time-honored practice, by simply sliding one or more of the cover slabs, to one side or the other, as denoted in the broken lines T and V.

To conserve the heat stored in the inner surfaces of the slabs, when thus slid to one side, the upper portion of the furnace is provided wlth an over-hanging brick platform, as 'Z, whereby the said'inner hot surfaces willnot be exposed to atmosphere.

limbs would be short-circuited;

Claims:

1. An electric furnace for fusing metals contained in a crucible, comprising a chamber, a zig-zag carbon resistor disposed along the bottom of said chamber to sustain the crucible, whereby heat may be transferred to the crucible by direct conduction.

2. An electric furnace for fusing metals contained in a crucible, comprising a chamber, a zig-zag carbon resistor disposed along the bottom of said chamber to sustain the crucible, the upper surface of said carbon resistor having ,a greater current-density characteristic than its lower surface, said resistor transferring heat to the bottom of the crucible by direct conduction.

3. An electric furnace for fusing metals contained in a crucible, comprising a chamber, a zig-zag carbon resistor disposed along the bottom of said chamber, the upper surface of said resistor sustaining the crucible,

and said resistor having vertically inclined sides for the transfer of heat therefrom by refraction to the crucible and the upper portion of the chamber. I

a. An electric furnace for fusingmetals contained in a crucible, comprising a chamber, a zig-zag carbon resistor disposed along the bottom of said chamber to sustain the crucible, whereby heat is transferred to the bottom thereof by direct conduction, said resistor having vertically inclined sides whereby heat is transferred therefrom by refraction to the crucible and the upper portion of the chamber.

This specification signed and witnessed this 29th day of November, A. D., 1918.

JOHN THOMSON.

Signed in the presence of- J. R. AGNEW, H. O. WEED. 

